Yoga Sutra 1.03 the Seer is established in his own nature

Then the power-of-consciousness rests in its own nature, as in the state of release. But when the mind is extraverted, though it is so, it is not so.

It has been said that yoga is inhibition of the mental processes, by which inhibition the true being of Puruṣa as the cognizer (boddhṛ) is realized. In which case some might suppose that with inhibition of the thoughts of objects, there would be inhibition of the subject, the cognizer, the Puruṣa, also. Then they would assume that it would not be sensible to try to attain Knowledge-of-the-difference, the means to release, and that the exposition of yoga, which aims at that Knowledge, would be futile. To show that inhibition of the mental process is not inhibition of Puruṣa, and to point directly to the result of Knowledge, the commentator says: What is Puruṣa, the cognizer of buddhi, in that state when there is no object for him? Then the seer is established in his own nature. When the mental process has been inhibited, then the power-of-consciousness rests in its own nature.

In that state, in the state of inhibition, when there is no object for him since the object, the mental process, is not there, what is the nature of Puruṣa, the cognizer of buddhi? Puruṣa is the cognizer of buddhi in the sense that he is aware of buddhi in its transformations as the forms of the mental processes. The nature of Puruṣa is simple awareness of them; the one who is aware is not different from the awareness. If the one who is aware were different from the awareness itself, he would be changeable and then would not be a mere witness who has objects shown to him. So his awareness and subjectivity are spoken of figuratively as if conforming to a mental process. But the sūtra will say, The Seer is sight alone (II.20).

Here it is being asked, what is the real being of that Puruṣa, the cognizer of buddhi (buddhi-bodhātman)? The compound buddhi-bodhātman means that his nature is pure awareness of buddhi. Is it a perishable nature? Or if it is real being (sad-bhāva), what sort of real being is it, and how does it come about?

Then the Seer is established in his own nature: when the mental process has been inhibited, then the power-of-consciousness rests in its own nature. Rests in its own nature means that it is like release. He is going to speak of that real being later (IV. 19) when he says Mind is not self-illumining, because it is itself something perceived. The phrase about resting in its own nature has been used in order to clear up any doubt as to what is its real being.

(Opponent) The sūtra is in definite terms, and it must follow that at some other time the power-of-consciousness is not so established, for otherwise the specification Then would be meaningless. And if at this other time it is not established in its own nature, there is the objection that it will be subject to change, because it will then have become associated with a different condition.

(Answer) But when the mind is extraverted, though it is so, it is not so. The first phrase though it is so shows that even in this time of extraversion, the power-of-consciousness is established in its own nature, it is not so shows that the specification of the time of extraversion has some meaning.